A power conversion device that converts power acquired from an overhead line to supply the converted power to a motor or an in-vehicle device is mounted on a roof of or under a floor of an electric railroad vehicle. The power conversion device contains a power convertor that converts input power by switching operation of a semiconductor element and outputs a desired alternating-current power. Since the semiconductor element generates heat during the switching operation, the power conversion device is provided with a plate-fin or pin-fin heatsink for releasing heat transferred from the semiconductor element. In order to improve cooling efficiency, the heatsink is arranged at a location where the heatsink is subjected to external air. The semiconductor element included in the power converter and the electronic component included in an output controller outputting a control signal to the power converter are arranged inside a housing of the vehicle not to be subjected to the external air in order to suppress or prevent malfunctions of the semiconductor element and the electronic component due to dust or moisture. As described above, a location of each component of the power conversion device arranged is determined in accordance with the necessity of cooling and the necessities of dust prevention and water proof.
In a power conversion system for an AC-DC dual current electric railroad vehicle disclosed in Patent Literature 1, a converter, an inverter, and a filter reactor that require forced air cooling and another component not requiring forced air cooling are placed together in the same housing. In the power conversion system for an AC-DC dual current electric railroad vehicle, the convertor, the invertor and the filter reactor are placed in a cooling air passage provided inside the housing and the another component not requiring forced air cooling is placed outside the cooling air passage. As in an underfloor device for a railroad vehicle disclosed in Patent Literature 2, the inside space of a housing of a power conversion device placed under a floor of a railroad vehicle is partitioned into a plurality of spaces by partition elements.